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Multi-Way Conventional loudspeakers with crossovers

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Old 1st September 2013, 02:03 AM   #9251
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Quote:
Originally Posted by Tom Danley View Post

...

The reason is the radiation of spatial q’s are what let you hear the source’s physical depth if your eyes are closed, are not part of the input signal. This works best with one speaker. Take the loudspeakers physical distance clues away and the sound, sounds “up close” on a dry mic recording or off somewhere in a reverberant recording. Listen in stereo and the speaker with spatial q’s produces a mono signal as a center phantom AND a right and left source. Take away the loudspeakers spatial q’s and you have a strong mono phantom and no apparent right or left source.

...
Hi Tom, I'm a little confused by the phrase "spatial q’s". Do you mean "spatial cues" in the subjective sense, or are does "q" refer to loudspeaker directivity in some way?

Going back to the "picture window" metaphor, I've heard speakers render the overall spatial impression (not the same as imaging, which refers to direct instrument locations) in several different ways.

If the speaker has serious issues with diffraction and long time decays, there's not much impression of a space at all. Everything hangs on a clothesline stretched between the two speakers, with no depth, height, or extra-width at all. Each instrument is a paper-thin cutout. If the driver layout is especially inept (old loudspeakers with scattershot driver locations and no mirror-imaging), even that is not accomplished, and the instruments blur and move around.

Modern designs with average time decays and slight attention paid to diffraction create a moderate space impression; extra-width impression happens on a few recordings with antiphase content (typically reverb), there's a bit of height (which is an artifact of two-speaker playback and not in the original recording), and depth impression correlates with lack of diffraction and a reasonable absence of low-level Class AB switching artifacts (which destroy space impression). MP3 and other lossy algorithms are impressively good at removing depth impression as well; I'm guessing the algorithm treats low-level, broadband reverb as noise, and removes it.

The better planar loudspeakers present a "through-the-window" impression, thanks to fast decay times, which preserves the time signature of the more important reverb cues in the recording, which in turn allows the ear/brain to cross-correlate the reverb cues with the first-arrival sounds, and derive distance information.

Point-source radiators with very low diffraction signatures can pull off an additional trick: disappearing completely as a sound source, since there's no cabinet-edge reflection for the ear/brain to detect. With the cabinet-edge reflection removed, there's no apparent cabinet, either in the original recording (microphone housings are far smaller than loudspeakers), or in the playback system. The picture-window impression disappears, and whole front half of the room merges with the acoustic of the recording environment.

It's been my experience that intelligibility is partly orthogonal to spatial impression: I've heard speakers with exceptional intelligibility and almost no spatial qualities at all, and speakers with truly remarkable spatial realism and only moderately good intelligibility. There are a handful of loudspeakers that combine both.

Last edited by Lynn Olson; 1st September 2013 at 02:25 AM.
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Old 1st September 2013, 02:28 AM   #9252
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Quote:
Originally Posted by Lynn Olson View Post
Hi Tom, I'm a little confused by the phrase "spatial qs". Do you mean "spatial cues" in the subjective sense, or are does "q" refer to loudspeaker directivity in some way?
Hi Lynn
Yes, sorry i was channeling my old boss who was a WWII acoustical from England and used that expression, read Cues.
It isn't the first time a couple of his expressions raise eyebrows haha.
Best,
Tom
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Old 1st September 2013, 07:03 PM   #9253
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I learned "Q" as a directivity index.
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Old 1st September 2013, 09:20 PM   #9254
Scott L is offline Scott L  United States
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Default Beyond the Ariel (as the thread unravels)

Lynn, and all others:

I have found relevance in this thread because I am also designing my "next" speaker system. I really want it to be my last. I'm not exactly sure where Lynn is at in his design process, but I wanted to introduce a thought, and that is that the mid-bass section of any speaker system (multi-way, of course) is going to be the predominant determination of sound quailty.
For discussion purposes, let's assume mid-bass includes lower mid-range such that 60-500Hz is what I am referring to. I have concluded that, in order to provide a realistic presentation, this area has to then again be covered by multiple drivers, perhaps even some sort of mechanical crossover as I feel a 4-way is the limit of complexity I care to indulge in.
Here's my thoughts: Since I am using a dedicated mid-range horn, it makes sense to me to also use a horn for lower mid-range. I am planning on using my pair of Altec 515-8G's, but since I am somewhat space limied I do not want a long horn;only enough to cover 150-600Hz max. (yes I may move my 500Hz x-over up to 600Hz, as I reckognize the center of energy in a musical programme as being 300Hz; 150-600 covers the octave either side). Because of this, I'll need more drivers to carry the "bass" section of the mid-bass. Perhaps two more 15 inchers per side, as I love the Grand Piano, but I really don't want to fool with the enourmous amount of wood/and/size required for a horn that by all rights, unless massively dampened, will have the propensity to resonate.
So, where does this lead us to, in, "Beyond the Ariel" ?
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Old 1st September 2013, 11:09 PM   #9255
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The AE TD-15M would also work well from 60-500hz+.
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Old 2nd September 2013, 02:35 PM   #9256
Scott L is offline Scott L  United States
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Default AE

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The AE TD-15M would also work well from 60-500hz+.
Thanks, Face

You have offered a relatively simple solution to what I have made complicated. I'm sure that driver would work fine in a smaller scaled loudspeaker system than what I am describing.
IMHO opinion, it will take at least 2x 15's per-side to generate enough acoustic power in the mid-bass to re-produce a Grand Piano realistically.
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Old 2nd September 2013, 02:56 PM   #9257
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From my experience a pair per channel of high quality (four is better but has other compromises) 15's will not keep up with a good recording or a quality compression driver crossed over 600 Hz or lower. Sure the PA systems sold today are configured that way because we all don't want to haul around a truck full of bass horns. A good bass horn loaded with a high quality driver is where to look and what to build if you really want to produce the low mid range and bass with realism. If you crossover low enough to the compression driver you can fold the horn to save space. Another take is a VOTT or JBL front loaded horn type system with the bass reflex ports in conjunction with multiple 15's or 18's to supplement below 100 Hz or so. A carefully matched example of this is a better compromise then just using direct radiator 15's in my experience. The lower you go with a front horn the more it approaches realism.
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Old 2nd September 2013, 03:52 PM   #9258
Scott L is offline Scott L  United States
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Default too tired when I wrote

Quote:
Originally Posted by POOH View Post
From my experience a pair per channel of high quality (four is better but has other compromises) 15's will not keep up with a good recording or a quality compression driver crossed over 600 Hz or lower. Sure the PA systems sold today are configured that way because we all don't want to haul around a truck full of bass horns. A good bass horn loaded with a high quality driver is where to look and what to build if you really want to produce the low mid range and bass with realism. If you crossover low enough to the compression driver you can fold the horn to save space. Another take is a VOTT or JBL front loaded horn type system with the bass reflex ports in conjunction with multiple 15's or 18's to supplement below 100 Hz or so. A carefully matched example of this is a better compromise then just using direct radiator 15's in my experience. The lower you go with a front horn the more it approaches realism.
This is exactly what I was trying to describe in my ealier post. I was just too tired when I wrote it to explain it right. I plan on using one horn loaded 15, an
Altec 515-8G AND in addition at least one additional pair of 15's EQ'd such that they only augment where the Altec unloads below and down to where it crosses to the dedicated SUBS.
We pretty much agree, except I think there is a point to where a horn is too large and we arrive at the law of dimishing returns. Just too big, bulky and
too much wood suseptable to resonating.
A few days ago, at a local audiophile coffee meet, my friend pointed out that 4 15's per side have the equivalent cone radiating area as a VOTT horn:
540 square inches (approx). My thoughts were........ BINGO !!
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Old 2nd September 2013, 04:08 PM   #9259
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Originally Posted by Scott L View Post
Lynn, and all others:

I have found relevance in this thread because I am also designing my "next" speaker system. I really want it to be my last
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Old 2nd September 2013, 04:09 PM   #9260
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